The present invention concerns capacitors for implantable medical devices, such as defibrillators and cardioverters, and more specifically to a method of manufacturing a capacitor stack for a flat capacitor.
Implantable defibrillators detect the onset of abnormal heart rhythms and apply corrective electrical therapy, specifically one or more bursts of electric current to the heart. A defibrillator includes a set of electrical leads, which extend from a pulse generator housing into the heart. Within the pulse generator housing are a battery for supplying power, monitoring circuitry for detecting abnormal heart rhythms, and a capacitor for delivering the bursts of electric current through the leads to the heart. Since defibrillators are usually implanted in the left region of the chest or in the abdomen, a smaller size device, which is still capable of delivering the required level of electrical energy, is desirable. Accordingly, smaller and more powerful capacitors are desirable.
One type of capacitor is a flat capacitor. Flat capacitors have a layered stack of capacitor elements. The stack includes a series of anode and cathode foil layers each separated by a separator layer. To ensure that a capacitor stack does not short out and that it takes up as little volume as possible it is important to carefully align each layer of the capacitor stack when constructing the capacitor stack.
The present system includes methods and apparatus to manufacture a capacitor stack so the stack is precisely aligned while optimizing the area and volume of the stack.
In one embodiment, a method of manufacturing a capacitor stack for a flat capacitor includes sequentially stacking a plurality of capacitor layers on top of each other such that each one of the plurality of capacitor layers is, in turn, a top layer of the capacitor stack, and continually applying a compression force between a bottom layer of the capacitor stack and the top layer of the capacitor stack until all of the plurality of capacitor layers have been placed.
One aspect provides an apparatus for forming a capacitor stack. In one embodiment, an apparatus includes a fixture for holding a plurality of capacitor layers defining the capacitor stack as each of the plurality of capacitor layers is placed onto the capacitor stack, and means for continually applying a compression force on the capacitor stack until each of the plurality of capacitor layers have been stacked.